The present invention is directed to a hollow cylindrical sleeve which can be removably mounted onto mandrels, bridge sleeves, or cylinders for use in printing, coating, or the like, and in particular to a thin-walled hollow, reinforced cylindrical sleeve having an integral compressible layer.
In flexographic printing operations, flat, flexible plates were hand mounted onto print cylinders by wrapping and adhering the plates to the underlying cylinder. Generally, the flat plate comprised a base layer having either a rubber layer with relief indicia or a photocurable polymer layer thereon. In some instances, a compressible layer was positioned between the base layer and rubber or photocurable layer to improve print quality. Such flat plates had the advantage that they could be relatively thin and flexible because they were to be directly mounted to the print cylinder. However, such mounting processes were labor intensive and slow.
More recently, hollow cylindrical sleeves have served as supports for various types of printing. In one existing flexographic printing process and product (commercially available in the United States from OEC Graphics, Inc. under the trademark SEAMEX), a photopolymerizable material in the form of a flat sheet is wrapped around a metal (such as nickel) or plastic sleeve whose surface has been primed with a heat activated adhesive. The sleeve and photopolymer material are then heated, bonding the photopolymer to the sleeve. The surface of the sleeve is then ground to a predetermined plate thickness. The plate may then be processed by registering a negative onto the sleeve, exposing the sleeve to radiation to cure exposed areas of the photopolymer, and then washing out unexposed portions of the photopolymer to leave a relief image for printing.
In other printing applications, including offset lithography, a rubber layer is applied to a base sleeve and vulcanized. The rubber may then be ground to thickness. Accordingly, for these applications, it is necessary that the sleeve be able to tolerate the high temperatures experienced during activation of adhesive and vulcanization of rubber. In both of these applications, the hollow cylindrical sleeve must be relatively smooth and stiff in order to be suitable for its intended support purpose and to provide a desired printing quality upon a substrate such as, for example, paper.
Hollow cylindrical sleeves of various configurations are known from U.S. Pat. Nos. 4,391,898; 4,503,769; 4,554,040; 4,601,928; 4,656,942; 4,812,219; 4,949,445; 4,963,404; 5,468,568; 5,819,657; 5,840,386; 6,038,971; and 6,038,975. Generally, these prior art sleeves consist of a plurality of associated concentric layers, typically an outer printing or surface layer and one or more underlying support layers.
For example, Anderson, U.S. Pat. No. 4,503,769, discloses a metal-coated, thin-wall plastic printing cylinder for rotogravure printing. An expanding mandrel containing journal bearings internally and laterally supports a metal coated, hollow, plastic cylindrical sleeve (glass fiber reinforced polyester or phenolic resin).
Van der Meulen, U.S. Pat. No. 4,949,445, teaches a cylindrical sleeve with a metal or plastic core which is covered with a compressible material onto which a perforated (stencil) printing sleeve may be mounted. Van der Velden, U.S. Pat. Nos. 4,601,928, 4,554,040, and 4,391,898, teach cylindrical printing sleeves formed on about a woven fabric mesh using sheets of photopolymer which are wrapped about the mesh core.
Vertegaal et al, U.S. Pat. No. 4,656,942, discloses a printing apparatus using flexible metal sleeves to transfer ink and a method of mounting the sleeves. The sleeves are made by electro depositing metal in a form that is very thin, readily collapsible, and imperforate. The outer surface of the sleeve is coated with a flexible, microcrystalline, wholly inorganic photoconductive material. One example of this type of material is sputtered ultra-pure cadmium sulfide.
Sattrup et al., U.S. Pat. No. 4,812,219, discloses a method of producing a surface sleeve for mounting on a plate cylinder in a printing process. A cylindrical sleeve made from an electrically conductive material such as nickel is mounted onto a supporting mandrel with a cylindrical outer surface. An inner metal layer is electrolytically deposited on the outer peripheral surface of the sleeve and an outer copper layer is electrolytically deposited on the inner metal layer. The printing pattern is etched directly on the copper layer or on a chrome layer covering the copper layer. Subsequently, after the engraving of the printing pattern, the opposite outer portions of the sleeve are removed due to the increased thickness of the metal layers.
Jenkins, U.S. Pat. No. 4,963,404, discloses a process for the production of a thin walled coated cylinder and an ink transfer roller. A thin-walled, seamless nickel cylinder is coated by plasma spraying a ceramic fluorocarbon polymer thereon. An adhesive layer of metal is applied between the surface of the cylinder and the coating. The adhesive layer consists of at least two metals reacting exothermally with each other under plasma spraying conditions.
Kühn et al, U.S. Pat. No. 5,468,568, is directed to a printing roller designed for a gravure printing process with a sleeve of fiber-reinforced thermoplastic which is then plasma sprayed to form a coating of copper or a copper alloy. A variety of fibers and plastics are disclosed for use in the sleeve, which is stated to have a wall thickness of less than about 3 mm.
Rossini, U.S. Pat. No. 5,819,657, teaches a carrier spacer sleeve for a printing cylinder. The patent contains a discussion of the use of thin sleeves in flexographic printing operations. Such thin sleeves are designed to be air mounted onto the carrier spacer sleeves to enable a printer to modify the effective diameter of printing cylinders for jobs of different print repeat lengths.
Hatch et al, U.S. Pat. No. 5,840,386, describes a sleeve that is adapted to be mounted onto a mandrel. The sleeve is used to transfer ink in anilox or gravure printing processes. The sleeve includes an inner layer, an intermediate compressible layer, and a metal outer layer. The inner layer may be fabricated from fiber-reinforced plastic and may be in the form of a DuPont Cyrel™ sleeve.
Fisher, U.S. Pat. No. 6,038,971 discloses a method and apparatus for producing a screen-printing stencil. A covering layer is applied to certain areas of a fine-mesh screen corresponding to a predetermined printing design. The screen is closed on the backside by a cylindrical support to prevent the covering liquid from passing through the screen. The support may be a thin walled metal cylindrical sleeve.
Hoffmann et al, U.S. Pat. No. 6,038,975, discloses a gapless sleeve for offset printing. The sleeve includes a roller core and a thin intermediate layer, which can be either a self-adhesive plastic sheet or a coating of plastic, metallic, or ceramic material.
The known hollow cylindrical sleeves however exhibit a number of constraints with respect to their manufacture and use. For example, one problem has been that one currently-used manufacturing process for such hollow cylindrical sleeves produces a seam in the sleeve which may affect the print quality of high quality flexographic printing. Other substrates such as nickel, zinc, copper, or other metal sleeves are much higher in cost and cannot effectively serve as consumable items. Another problem is that current polyester sleeve materials are not able to withstand the high temperatures required to vulcanize rubber print layers.
None of the thin-walled hollow cylindrical sleeve constructions of the prior art solely utilizes a reinforcing fibrous material to provide a low-cost product which is capable of withstanding the heat of vulcanization of rubber and which has the capability of being mounted onto a carrier in an airtight manner. Conventional hollow cylindrical sleeves having a base layer of fabric have seen only limited use due to their lack of holding strength on a cylinder as well as their lack of air-tightness required for proper mounting of the sleeve. A thin-walled fiber-reinforced hollow cylindrical sleeve would be advantageous because of low manufacturing costs and could be used as a consumable item when paired with either a photopolymer plate or a rubber layer.
Therefore, there remains a need in the art for an inexpensive, thin-walled fiber-reinforced hollow cylindrical sleeve which does not suffer from the problems of prior art sleeves.